Aerial pipeline abandonment reaches new heights

The world has changed since the 1970s, and the oil and gas industry is no exception. Improvements in safety, training and technology have changed the way we approach complex projects for the better. At Chet Morrison Contractors, we recently found ourselves faced with a challenge that had no obvious precedent: safely removing and dismantling an aerial pipeline 22 inches in diameter suspended from cables 73 feet above fast-moving water.

Originally installed in the 1970s, this pipeline traditionally had workers in boxes up to 80 feet in the air — a level of risk that is now less tolerable. Given the right combination of creativity and expertise, it’s also avoidable, which we proved by completing the country’s first-ever aerial pipeline abandonment and dismantlement.

The key to success with a project of this nature is planning. By working closely alongside our partners, we developed a work scope that was efficient and met stringent regulatory and safety requirements. With no other examples of this kind of work to reference, we had to start from scratch.

The pipeline spanned more than 800 feet between inverted Y towers on the banks of Wax Lake Outlet, located in South Louisiana’s Atchafalaya Bay. Bringing down the pipeline, cables and towers would be no easy feat, but the biggest risk would come from putting workers at height to perform the necessary cuts while also accounting for the fast-moving water below. The site itself was also problematic, with nearby levees making it difficult to bring in the necessary tools for a project of this size. Finally, we had to account for the many challenges (expected and not) we faced, such as unsprung energy storage, environmental concerns and inclement weather.

We developed a plan that could meet these challenges and worked closely with our partners to ensure every step of the process was managed safely. For site stability, we installed interlocking mats on both banks to provide support and traction for vehicles and workers. A fit-for-purpose equipment spread included several of our barges capable of supporting a crane and transporting 50-foot pipe segments after removal.

In order to lower the risks of cutting at heights, we identified a unique solution that avoided the task completely by contacting the original designer of the aerials to find out how they were installed. This gave us the necessary insight to reverse-engineer the project and tweak it as needed for improved safety and efficiency.

With the cables safely cut and the pipe ends excavated, nitrogen was pumped into the pipeline to dewater each one before lowering each at a 45-degree angle and dropping the pipeline end onto the deck of the barge. By slowly raising or lowering the tower, the crew was then able to cut each pipe into segments on the deck.

An additional project obstacle was recreational boat traffic from a nearby public boat launch. In order to mitigate the disruption of local activities, we worked with local law enforcement to help manage the waterway. The official boats and lights proved effective at cautioning vessels. Through close coordination, recreational boats were escorted safely through to the other side without severely impacting the project or the area.

Lessons learned

Taking what we knew from other pipeline abandonment work and adding in the necessary engineering know-how, we planned for every possibility and mitigated risk at every step. Teams carefully coordinated to make sure we were prepared for anything, and project managers were always on-site to supervise and manage any necessary changes at each stage of the project. Ultimately, the success of the project — completed on schedule and incident-free — was due in large part to that teamwork and our collective experience and expertise.

For more information, visit www.chet morrison.com or call (985) 868-1950.